Automatic tester for testing resistance and inductance of coil windings

ABSTRACT

A coil winding tester has a bridge circuit with two variable resistors connected to the two adjoining sides and two standard coil windings connected to the other two sides. A a power source, it further has D.C. and A.C. connected in parallel to the bridge circuit. A coil winding to be tested, when connected to this invention&#39;&#39;s circuit, causes a control signal to set one of the thyristors to work an electric magnet, connected to the A.C. power source, via another thyristor. This electric magnet is linked to a change-over switching device to disconnect automatically, via two thyristers, the circuit for the standard coil and forms a circuit for the test coil for testing/measuring the inductance and resistance of the test coil by a galvanometer.

United States Patent [191 Azuma AUTOMATIC TESTER FOR TESTING RESISTANCEAND INDUCTANCE OF COIL WINDINGS [76] Inventor: Koichi Azuma, 22 Miyuki,

Shikamaku,I-Iimeji, Japan [22] Filed: July 2, 1971 [21] Appl. No.:159,260

[52] US. Cl ..324/59, 324/DIG. l [51] Int. Cl. ..G0lr 11/52 [58] Fieldof Search ..324/59, DIG. l

[56] References Cited UNITED STATES PATENTS 2,540,589 2/l95l Long..324/DIG. 1 3,445,764 5/1969 Tedeschi ..324/59 FOREIGN PATENTS ORAPPLICATIONS 1 11,171 7/1944 Sweden ..324/59 GALVANOMETER [451 May 22,1973 451,094 7/1936 Great Britain ..324/59 Primary ExaminerStanley T.Krawczewicz AttorneyEmest G. Montague [5 7] ABSTRACT A coil windingtester has a bridge circuit with two variable resistors connected to thetwo adjoining sides and two standard coil windings connected to theother two sides. A a power source, it further has DC. and AC. connectedin parallel to the bridge circuit. A coil winding to be tested, whenconnected to this inventions circuit, causes a control signal to set oneof the thyristors to work an electric magnet, connected to the A.C.power source, via another thyristor. This electric magnet is linked to achange-over switching device to disconnect automatically, via twothyristers, the circuit for the standard coil and forms a circuit forthe test coil for testing/measuring the inductance and resistance of thetest coil by a galvanometer.

1 Claim, 3 Drawing Figures Patented May 22, 1973 INV EN TOR.

AUTOMATIC TESTER FOR TESTING RESISTANCE AND INDUCTANCE OF COIL WINDINGSThe present invention relates to a coil winding tester, and moreparticularly, to an improved and simplified coil winding tester fortesting/measuring the resistance and inductance of test coils, incomparison with a standard coil winding of known value, by the use of anautomatic change-over circuit device equipped with thyristers and abridge circuit connected in parallel to A.C. and D.C. power source.

It is one object of the present invention to provide a new andconvenient means of testing/measuring the inductance and resistance ofcoil windings to be tested by automatically switching the circuit forone of the two standard coil windings, each being connected to each sideof the two sides of the bridge circuit with A.C. and D.C. supplied inparallel thereto, over to the circuit for the test coil.

It is another object of the present invention to provide an automatictester for testing resistance and inductance of coil windings whichcomprises a bridge circuit including two variable resistors connected,respectively, to two adjoining sides thereof and two standard coilwindings, first and second, connected to the other two sidesrespectively, and D.C. supply with an amperemeter and also D.C. supplywith a condenser connected in parallel with the bridge circuit. When atest coil winding is connected, the control signal across the negativepole and gate of the second thyrister makes the third thyrister work, soas to energize the electric magnet to operate the change-over switch,and the second standard coils circuit is switched over, via the firstand second thyristers, to the circuit for the test coil winding fortesting thereof.

With these and other objects in view, which will become apparent in thefollowing detailed description, the present invention will be clearlyunderstood in connection with the accompanying drawings in which:

FIG. 1 is a fundamental circuit for the present invention;

FIG. 2 shows the circuit with the first and second standard coilwindings connected therewith; and

FIG. 3 shows the circuit with a coil to be tested connected therewith.

Referring now to the drawings, an embodiment of the present inventionfor automatic testing of resistance and inductance of coil windings isillustrated as comprising a bridge circuit, which has two variableresistors l and 2 fitted to the two adjacent sides and also two standardcoil windings 3 and 4, constituting other sides of the bridge circuitthrough connections to connecting terminals 3', 3", 4 and 4".

D.C. and A.C. power sources are connected in parallel to the bridgecircuit, with a D.C. amperemeter 6 and a condenser 8 inserted,respectively. When the coil winding to be tested isconnected asillustrated in FIG. 1, this causes a third thyrister 24 to energize anelectric magnet 28, connected to an A.C. power source, by a controlsignal across the negative pole 23 and the gate 22 of a second thyrister20, whereby change-over switches 10 and 13 work to switch off thecircuit for the second standard coil winding through the actions offirst and second thyristors l6 and 20.

According to the present invention, the first and second standard coils3 and 4 of equal value are connected to the terminals 3', 3", 4 and 4"in order to form the bridge circuit as illustrated in FIG. 2. Thiscircuit is then balanced by adjustment of the variable resistors 1 and2, and in that fixed and balanced state the coil winding 5 to be testedis connected to the test terminals 5' and 5". Through the coil winding 5and with an internal resistance across the negative pole 23 and the gate22 of the second thyrister 20, the control signal is given across thenegative pole 27 and the gate 25 or positive pole of the thirdthyrister, whereby the conductive state across the positive and negativepoles 25 and 27 works the magnet coil 28, to set the changeover switch10, which is connected to the terminal 3" for the first standard coilwinding 3 and a terminal 5" for the test coil winding 5, andsimultaneously to set the change-over switch 13, which is connected withthe power source for the bridge circuit.

This arrangement, accordingly, connects the coil winding to be tested 5to the testing circuit via the first and second thyristers 16 and 20 inplace of the second standard coil winding 4, which previouslyconstituted a part of the bridge circuit.

The switch 10, one of the change-over switches, equipped with two-waycontact points, is connected to one of the connecting terminals 3" ofthe first standard coil winding and also to one of the connectingterminals 5' of the coil winding to be tested 5, with one contact point11 being connected to the connecting terminal 4' of the standard coilwinding 4 and the other contact point 12 being connected to the gate 18of the first thyrister 16. The other change-over switch 13 is connectedto the positive power source for the bridgecircuit, with one contactpoint 14 being connected to the connecting terminal 4" of the secondstandard coil winding 4 and the other contact point 15 being connectedboth to the negative pole 19 of the first thyrister 16 and the gate orpositive pole 21 of the second thyrister 20. Furthermore, the connectingterminal 5" of the coil winding to be tested is connected with both thepositive pole 17 of the first thyrister 16 and the negative pole 23 ofthe second thyrister 20, while the gate 22 of the second thyrister 20 isconnected to the gate 26 of the third thyrister 24 through an auxiliaryresistance 30 and an A.C. amperemeter 29.

Further, a galvanometer 34, connected across the adjoining point of thevariable resistor 1 and 2 and a connecting terminal 3" of the firststandard coil winding 3, gives a reading for balancing the bridgecircuit. The A.C. current needed for the circuit is first adjusted by aresistor 32 and supplied thereto.

In FIG. 1 a safety switch is provided to cut the circuit for thegalvanometer 34 off the bridge circuit momentarily together with thechange-over switches 10 and 13 when the second standard coil winding 4is electrically replaced by the coil winding to be tested. A safetyresistor 36 is provided for A.C. power supplied to the bridge-circuit.

Now to show an example of an embodiment of the present invention, twostandard coils, inductance of which is 0.78 H, are connected across theterminals 3', 3" and 4', 4", and the balance of the bridge-circuit isobtained by manipulating the variable resistors l, 2 with the breakerfor galvanometer 34 on.

When a coil winding, of which inductance is known prior, 0.78I-I, isconnected across the terminals 5', 5" for testing, this coil windingreplaces the standard coil winding in the bridge circuit. After thevalue of auxiliary resistor 30 connected to the A.C. amperemeter 29 hasbeen set in such a way as to have the said amperemeter 29 show a readingof 100 with the afore-mentioned known coil winding of 0.78 H and areading of 40 with inductance of 1.0 H (in this case the resistance is10 a coil of unknown inductance is then connected to the test terminals5 and 5".

Inasmuch as a coil winding 5 of high inductance allows more flow ofcurrent than another with lower inductance, the arm of the galvanometer34 then swings to the minus side in case an error of the coil winding tobe tested is over and above plus 0.1 H, when compared with the standardcoil winding, and swings less, when the error is less. In this way,inductance and resistance of a test coil winding can be tested incomparison with the standard coil winding.

To describe in more detail, when the circuit for the standard coil 4 ischanged over to that of a test coil 5 connected to the test terminals 5'and 5", the A.C. current is thus connected to the plus side of the D.C.source 7, of the bridge circuit and is connected across the positive andnegative poles 25, 27 of the third thyrister 24, which allows a certainamount of A.C. current to the gate 26, whereby A.C. current, regulatedby the auxiliary resistor 30, flows across the negative and positivepoles 23, 21 through the gate 22 of the second thyrister, and isconsequently coupled with D.C. to make it possible, together with A.C.connected to the plus side of the bridge-circuit as mentioned earlier,to test the inductance of test coils.

Thus, the reading of the A.C. amperemeter indicates according to varyingdegrees of inductance to be measured.

From the foregoing, it will be clear that, according to the presentinvention, the testing/measuring of the inductance of the test coilwindings can be performed, in comparison with the standard coil winding,by the A.C. shunt coupled with D.C. through the actions of thyristersfitted to the circuits of the device, thereby making it possible totest/measure D.C. inductance of coil windings by means of a method fortesting/measuring A.C. inductance. Change-over from the standard coilcircuit to the test coil circuit is more accurately performedautomatically, with precise testing made possible and the overallhandling of the device simplified greatly. Unlike other prior art coilwinding testers equipped with highly complicated devices and circuitssuch as synchroscopes and oscillatory circuits, the present inventionprovides a superior precise testing- /measuring of high sensitivity ofindividual coil windings to be tested with a simplified circuitstructure.

While I have disclosed several embodiments of the present invention, itis to be understood that these embodiments are given by example only andnot in a limiting sense.

I claim:

1. A device for automatic testing resistance and inductance of coilwindings, comprising in combination a bridge circuit having two variableresistors connected respectively, to the two adjoining sides thereof anda first and second standard coil connected, respectively, to the othertwo sides of said circuit,

a D.C. power source with an amperemeter and an A.C. power source with acondenser, which are connected to the bridge circuit in parallel,

a first, a second and third thyrister operatively connected togetherconstituting a thyrister circuit,

an electro-magnet connected to said third thyrister,

a switch means controlled by said electro-magnet,

said second thyrister including a gate and a negative pole,

means for applying a control signal across the negative pole and thegate of said second thyrister to actuate said third thyrister toenergize said electromagnet and operate said switch means,

test terminals connected across a coil to be tested and to said firstand second thyrister,

and said switch means operatively connected to said second standard coiland disconnecting the latter when in an open condition.

1. A device for automatic testing resistance and inductance of coilwindings, comprising in combination a bridge circuit having two variableresistors connected respectively, to the two adjoining sides thereof anda first and second standard coil connected, respectively, to the othertwo sides of said circuit, a D.C. power source with an amperemeter andan A.C. power source with a condenser, which are connected to the bridgecircuit in parallel, a first, a second and third thyrister operativelyconnected together constituting a thyrister circuit, an electro-magnetconnected to said third thyrister, a switch means controlled by saidelectro-magnet, said second thyrister including a gate and a negativepole, means for applying a control signal across the negative pole andthe gate of said second thyrister to actuate said third thyrister toenergize said electro-magnet and operate said switch means, testtermiNals connected across a coil to be tested and to said first andsecond thyrister, and said switch means operatively connected to saidsecond standard coil and disconnecting the latter when in an opencondition.